1. Field of the Invention
The present invention relates to a method for forming an SOI substrate and an apparatus for forming the SOI substrate.
2. Description of the Related Art
Instead of a silicon wafer which is manufactured by thinly slicing an ingot of a single crystal semiconductor, a semiconductor on insulator (hereinafter abbreviated to SOI) substrate in which a thin semiconductor layer is provided on an insulating surface is manufactured and is used for manufacturing semiconductor integrated circuit elements or the like.
As a method for forming an SOI substrate, a hydrogen ion implantation separation method is known (for example, see Patent Document 1). A hydrogen ion implantation separation method is performed as follows: first, an insulating thin film (e.g., a thermal oxidation film) is formed on a surface of a bond substrate (e.g., a single crystal silicon wafer) and hydrogen ions are added from a face of the bond substrate, so that a microbubble region in which dangling bonds of silicon are terminated by added hydrogen ions is formed at a predetermined depth which is the neighborhood of the face. Then, another substrate (hereinafter, referred to as a base substrate), e.g., a silicon wafer or a glass substrate, is attached to the surface at the periphery of which has the microbubble region and heat treatment is performed. Accordingly, hydrogen ions in the bond substrate are concentrated in the microbubble region and a cleavage phenomenon occurs in the microbubble region. Then, the bond substrate is removed from the base substrate, so that part of the bond substrate which is more on the one of the surfaces side than the cleaved surface (hereinafter, referred to as a thin bond layer) can be transferred to the base substrate with the insulating thin film interposed between the bond substrate and the base substrate.